Platinum-containing catalysts and method of preparation thereof



Aprll 28, 1959 CONNOR, JR ET AL 2,884,374

PLATINUM-CONTAINING CATALYSTS AND METHOD OF PREPARATION THEREOF,

Filed Oct. 22, 1954 2 sheetysheet 1 Figure l.

3o 4o 6O so- I00 D+L of Silica-Alumina Component James E. Connor,Jr.

Clifford S. Shipley INVENTORS A TTES T:

April 28, 1959 J. E. CONNOR, JR, ET AL Filed Oct. 22, 1954 PREPARATIONTHEREOF 2 Sheets-Sheet 2 m f I E CatalystS O 2 z 50 r 3 EH 0 c 4- O 3 '9l'ne C a g 30 I 2 8 20 Q 5 Catalyst A 3 5 IO '4': O

Minimum Bed Temperature Increase C 2 40. I g S catalyst S 2 z 3 :3 3o *32 m g 2 Q z E 2 line D v 2 .2 m 0 IO E 0 Catalyst A U 0 f 6 O 2 0 I 2 34 5 Clear Octane Number Decrease FIG?) ATTEST:

M). PM

' James E. Connor,Jr.

Clifford S. Shipley INVENTORS nited PLATINUM-CONTAINING CATALYSTS ANDMETHOD OF PREPARATION THEREOF Application October 22, 1954, Serial No.463,851 7 Claims. (Cl. 208-138) This invention relates toplatinum-containing catalysts and to their method of preparation anduse, and more particularly to platinum-containing catalysts having ahigh stability prepared from a specific complex compound of platinum andto the use of such catalysts in reforming processes.

In the past few years the octane requirements of automotive engines havebeen steadily increased. Furthermore, the percentage of various makes ofcars requiring premium fuels of exceptionally high octane in order toobtain the performance built into them by the manufacturers has beenincreased. For example, in the year 1950 a fuel of 90 octane number wassufiicient to satisfy the requirements of any engine. By 1954, fuels of94.5 to 95 octane were necessary for efiicient operation of all enginesand the number of units requiring such fuels had increased theirproportion and numbered several million, thus not only was an extremelyhigh octane fuel required but much larger volumes were likewiserequired. In addition, it has been predicted by many automotive andpetroleum experts that by 1958 fuels of 98 octane number will berequired in even greater quantities since an even higher percentage ofengines will require such fuels.

This problem is aggravated by the fact that in order to produce thenecessary quantities of fuels it is necessary that many sources of crudepetroleum be used which are not particularly suited for production ofthese extremely high octane gasolines. For many years petroleum refinersfound the necessary quantities of motor fuels of the required octanelevel could be produced by combining the products of catalytic cracking,thermal cracking and thermal reforming with straight run naphthas.However, a number of years ago it was found necessary to up-grade inoctane the thermal and straight run products. In order to accomplishthis, refiners turned to catalytic reforming.

Straight run and thermally cracked gasoline fractions are composed ofstraight chain, slightly branched chain, cyclic paraffins and olefins,all of which have relatively low octane values, together with only minoramounts of aromatics.

Several reactions are possible whereby the octane value of straight runand thermally cracked gasoline fractions may be increased. Thesereactions include the isomerization of straight chain and slightlybranched chain hydrocarbons to more highly branched chain compounds, theisomerization of the cyclic saturated compounds (naphthenes) to sixcarbon ring structures suitable for dehydrogenation to the correspondingaromatics, the dehydrogenation of six carbon ring naphthenes to thecorresponding aromatics, the conversion of paraffins to aromatics bydehydrocycli'zation, and the selective cracking of high molecular weighthydrocarbons to compounds of lower molecular weight in the gasolineboiling range.

Although many compositions have been proposed as being useful inpromoting one or more of the above reactions, only certain platinumimpregnated acidic metal oxide component catalysts are known to becapable of successfully promoting all of the desired reactions in a iceratio which will give the greatest octane improvement with the lowestloss in yield. One example of such a catalyst contains silica combinedwith alumina as the acidic metal oxide component. Other acidic metaloxide components which may be impregnated with platinum for use in thisinvention include: silica-zirconia, silicaalumina-zirconia,silica-magnesia, silica-alumina-magnesia, silica-thoria,silica-alumina-thoria, alumina-thoria, and similar oxide combinations.These metal oxide components are characterized by having exchangeablehydrogen ions in their structure. Their preparation and properties havebeen published Widely both in patents and in technical literature.Therefore, for purposes of brevity, this information will not bereiterated here. Likewise, the proportions of the various individualoxides which can be combined to produce the acidic metal oxide componentmay vary over relatively wide ranges as has been set forth in the priorpatent and literature art.

It is necessary when using these catalystsin a reforming operation,however, to have present rather large amounts of hydrogen whichfunctions to maintain the catalyst in a clean condition, free of cokeand carbonaceous deposits which would substantially deactivate thecatalyst if allowed to accumulate. Since there is a net production ofhydrogen in the over-all reforming reaction, there is no serious problemwith respect to hydrogen supply. To make the hydrogen effective,super-atmospheric pressures must be used or, in other words, thehydrogen partial pressure must exceed one atmosphere.

The dehydrogenation reaction is one of the most rapid of the reformingreactions and, therefore, under most operating conditions, equilibriumcan be readily reached between the naphthenes and the aromatics. Since,however, the volume of the products exceeds the volume of the reactants,the reaction is of course affected by pressure in the reversedirection-that is, the formation of aromatics is decreased as thepressure is raised at a constant reaction temperature. In addition, itis well-known that at a constant pressure, as the reaction temperatureis increased, the equilibrium shifts in the direction of higher aromaticproduction. It follows, therefore, that since it is highly desirable tohave the equilibrium as far as possible in the direction of maximumproduction of aromatics and, since super-atmospheric pressures must beused, higher temperatures must also be employed.

. To summarize the foregoing: (a) hydrogen at superatmospheric pressuresis necessary to maintain the reforming catalyst in a clean condition,(b) dehydrogenation of naphthenes to aromatics produces hydrogen and inaddition furnishes an important increment of octane improvement, (c)equilibrium considerations require the use of elevated temperatures toproduce the maximum quantities of aromatics and hydrogen at thesuperatmospheric pressures, (d) isomerization reactions must be promotedto a maximum extent within the same range of conditions where maximumaromatic formation is realized, and (e) cracking must be controlled toprevent formation of hydrocarbons boiling below the gasoline range. Whenall five of these requirements are met simultaneously in a reformingprocess, that is when all of the desired reactions are in proper ratioone to the other, there results the optimum yield-octane relationshipfor the process.

Although several catalysts have been described in the prior art whereinone of the abovementioned acidic metal oxide components has beenimpregnated with platinum,

these catalysts have all been subject to a common disadvantage, namely,that they cannot be used to produce or higher CFRR octane number fuelscommercially in plant scale operations. Where it is said that an enginerequires a 95 CFRR octane number gasoline, it is of course apparent thatthis level may be reached by adding tetraethyl lead to a base stock inamounts up to 3 cc. per gallon. Thus, the clear (no tetraethyl lead)CFRR octane number of the catalytically reformed product may range.between,82 and. 84 CFRR octane level and the 95 level reached byaddition of 3 cc. of tetraethyl lead per gallon. Obviously since 3 cc.of. tetraethyl lead per gallon is the. maximum amount for automotivefuel per mitted by law,,it is desirable to produce a base stock having aclear CFRR octane number of about 85 to 36 such that a lower amount, ofthe order of 2.5 cc. tetraethyl leadper gallon is required to producethe 95 octane number motor fuel. Moreover, since the incrementalincrease in octane number which can be obtained by addition oftetraethyl lead decreases asthe octane level increases', ,it is,necessary, for example, to have base stocks ofalmost 90 ,CFRR clearoctane number to produce a 981CFRR octane number by additiomof. 3 cc..tetraethyl lead per gallon. I Furthermore,;very recently it has beenfound that large amounts of tetraethyl lead; sometimes produceundesirable engine performance because of such phenomena as surfaceignition. to produce the required 95 and higher octane level fuels thecatalytically reformed product must have a CFRR clear octane number offrom about 86 to 90.

In order to produce the 95 octane number fuels and higher with thesecatalysts under continuous operation it has been found; necessary to usehigh initial reaction temperatures to reach the 86 to 90 clear octanelevel. With these high temperature levels, the activity of thesecatalystsdeclines rapidly with use and in order to maintain the requiredoctane level, the reaction temperature must be raised still furtherwhich results in an even more rapid decline in activity. The net resultof these operations is that the catalysts have extremely short lives,making them economically unfeasible for use in commercial operations.

This decline in activity is manifested by a decline in ability of thecatalyst to promote the dehydrogenation reaction, that is, theconversion of naphthenes to aromatics, and in the ability of thecatalyst to promote the isomerization reaction at the'temperature levelsrequired for optimum dehydrogenation. In addition, as thedehydrogenation ability of the catalyst declines, its ability to controlthe hydrocracking reaction likewise disappears with the result thatuncontrolled cracking occurs and yield of gasoline boiling range productdecreases. The measure of a catalysts resistance to this decline inactivity will herein after be referred to as its stability.

Since the aforementioned catalysts suffered universally from the samedisadvantage, namely, lack of stability at severe reforming conditions,it is reasonable to assume thatthis characteristic was due to aninherent property of suchcatalysts, to a common defect introduced intheir preparation, or to a combination of these factors.

It is an object of the instant invention to provide a catalyticreforming process which will produce high octane gasoline at high yieldsemploying a catalyst which is stable under the required reformingconditions.

It is an additional object of this invention to provide a catalyst whichwill promote dehydrogenation of hydrocarbons and isomerization ofhydrocarbons and simultaneously control the hydrocracking reaction underall reforming conditions.

It is a further object of this invention to provide a reforming catalystwhich is stable under severe reforming conditions.

Additional objects will be apparent from the following description.

In accordance withthe present invention an acidic metal oxide componentwhose activity for the cracking of hydrocarbons has been altered istreated with an aqueous solution of platinous tetramminohydroxide toimpregnate platinum thereon in the form of the complex cation andthereafterthe treated component is dried and treated Consequently, inorder at elevated temperatures to convertthe platinum compounds tometallic platinum.

The acidic metal oxide components which are impregnated with theplatinum complex include silica and at least one metal oxide from thegroup consisting of alumina, zirconia, magnesia, and thoria. In general,an acidic metal oxide component having a catalytic cracking activity inthe range between 20 and 65 distillate-plus-loss as measured accordingto the method of Birkhimer, Macuga, and Leum, in A Bench Scale TestMethod for Evaluating Cracking Catalysts, Proceedings of the AmericanPetroleum Institute, Division of Refining, volume 27 (III), page (1947),is required. Various other methods of measuring the catalytic crackingactivity of such acidic metal oxide components have been described inthe literature. A summary of the most widely used methods, including theBirkhimer et al. method, appearsin Catalyticv Cracking Techniques in,Review, by Marshall Sittig, Petroleum Refiner, pages 274-275, volume 31,No. 9 1952). The Birkhimer et al. reference mentioned above gives acomparison of several methods, therefore, if it is desired to comparethe activity as described in terms of the Birkhimer et al. D+L withother activity measurements, it is only necessary to refer to thecomparisons mentioned in such review.

According to the Birkhimer et al. D+L (distillate-plus loss) activitymeasurement method, it would be possible to have a theoretical maximumD+L of 100. However, in general, for a fresh silica-alumina crackingcatalyst the maximum D+L will range between 90 and 95. Since the othercatalytic activity measurement methods which employ a D+L measure givemuch lower values for a fresh silica-alumina cracking catalyst, usuallyof the order of 45 to 65 depending upon the particular test, it isapparent that when one specifies a D+L scale having practicable maximumactivity of 90 to the Birkhimer et al. test is being employed.

Various methods of altering the cracking activity of acidic metal oxidecomponents have been disclosed in the prior art. For example, the acidicmetal oxide may be treated with steam at temperatures of from 900 F. to1400 F. at pressures ranging from atmospheric to several hundred poundsper square inch for a period of time sufiicient to provide the desireddegree of alteration. Other methods may be used for modifying thecatalytic activity of such components; for example, by varying theamount of the metal oxide combined with the silica or by incorporating achemically combined alkali metal in the component- As has been pointedout, the method of preparing acidic metal oxide components by combiningsilica with various metal oxides are well known. A particularlydesirable method of preparing a silica-alumina component involves addingsulfuric acid to commercial water glass in proportions to precipitatesilica hydrogel; the silica hydrogel is washed with acidulated water toremove sodium ions, after which the hydrogel is dispersed in asufiicient amount of an aqueous solution of aluminum sulfate of suitableconcentration and ammonium hydroxide is added to precipitate alumina toform a silica-alumina component containing 13 percent by weight ofalumina. The silica alumina component is then washed, dried, calcined atelevated temperatures and formed into pellets. Such a component willhave a D+L of from 90 to 95 in terms of the Birkhimer et al. D+Lmeasurement set forth above. Similar methods of preparing the othercomponents mentioned herein may be used. Likewise, the proportions ofthe metal oxides may be varied in accordance with prior art teachings.

Further, in accordance with the present invention, one oftheabove-mentioned acidic metal oxide components having a crackingactivity within the desired D+L range is contacted with a small excessof an aqueous solution of platinous, tetramminohydroxide. In general, aratio of 1,2 cc. of aqueous solution per gram of catalyst is pre ferred.This solution and the metal oxide component mixture is then heated to anelevated temperature, generally to about the boiling point of thesolution, and is held at this temperature for a period of time which mayrange from about 4 hours to 24 hours. Treating at temperatures of 210 F.to 212 F. for a period of about 4 hours is in many cases sufficient,however, in some cases additional improvement of the catalyst has beenfound when the heating has been continued from 18 hours up to 24 hours.It has been noted also that if the temperature is increased as byheating under superatmospheric pressures, the heating time can beshortened. If necessary, distilled or deionized water should be added tothe solution during the heating step to replace any Water lost byevaporation. After the heating step, the spent solution is drained fromthe impregnated metal oxide component and the impregnated componentpreferably is dried to remove excess moisture. The dried impregnatedcarrier then is subjected to known conventional methods for decomposingor reducing the platinum complex to produce metallic platinum on themetal oxide components. Preferred methods for accomplishing the latterstep include calcination with air or reduction with hydrogen at elevatedtem peratures.

The compound, platinous tetramminohydroxide, is believed to have theformula:

The portion of the compound within the brackets is the complex platinumcation wherein the platinum has a valence of +2. It is believed thatduring the initial step of treating the acidic metal oxide component,the complex cation replaces hydrogen ions in the lattice structure ofthe metal oxide component, which hydrogen ions in turn are neutralizedby the hydroxide ions of the platinous tetramminohydroxide. This beliefis substantiated by the fact that the platinum concentration of thetreating solution drops very rapidly to a low value which remainsconstant during the subsequent heating step.

It is one of the additional advantages of the instant invention thatsince the only by-product of the impregnation is water the solutionremaining after the impregnation may be fortified with additionalplatinous tetramminohydroxide and used for treating an additionalquantity of acidic metal oxide component. In prior art methods sincethere were other by-products of the impregnation step, it Was necessaryto recover the platinum from the spent irnpregnating solution before itcould be used for impregnating an additional quantity of an acidic metaloxide component.

The concentration of platinous tetramminohydroxide can be adjustedaccording to the desired amount of platinum to be placed on the metaloxide component. It has been found experimentally that for the acidicmetal oxide components above-mentioned an amount in excess of 95 percentof the platinum content of the solution is exchanged onto the basecomponent. Therefore, if it is desired to produce a finished catalystcontaining 0.45 percent platinum, approximately 0.02 molar solution ofthe platinous tetramminohydroxide should be used with a ratio of 1.2 cc.of solution per gram of metal oxide component.

In the preparation of the catalysts of the instant invention, the amountof platinum which is desired on the acidic metal oxide componentgenerally ranges from about 0.1 percent to 2.5 percent, although it isof course possible to deposit higher percentages or lower percentagesmerely by adjusting the concentration of the solution of platinoustetramminohydroxide.

The impregnated acidic metal oxide component is preferably dried atconventional temperatures, such as those ranging between about 212 F.and 325 F., using ordinary commercial methods such as tumble drying ordrying with hot air or nitrogen or similar gas. After removing theexcess moisture, the impregnated metal oxide component is subjected toconventional methods for decomposing or reducing the platinum complex toproduce metallic platinum on the oxide component. For example, this maybe air calcination at temperatures ranging between about 600 F. and 1000F.; preferably, however, between about 650 F. and 750 F. When hydrogenis used to reduce the platinum to the metallic state, temperaturesranging between 450 F. and 1000 F. may be used.

It has been pointed out that the aforementioned prior art commercialreforming catalysts have been found to be incapable of continuouslyproducing commercial quantities of high octane fuel, for example, in therange of octane or higher. In order to reach the required high octanelevels using prior art catalyst compositions, it is necessary toinitiate the reaction at an extremely high temperature level. These hightemperatures in themselves are an extremely important cause ofdeactivation of these catalysts, and produce an extremely rapid decreasein the ability of the catalysts to promote the desired reformingreactions in the proportions required for elficient reforming at thehigh octane levels. Thus, after a very short period at the high initialtemperature levels, the prior art catalysts were found to be no longercapable of producing a product at the required octane level obtained atsuch initial reaction temperature. Inasmuch as in a commercial unit theonly condition which can be varied readily is temperature, this decreasein the ability of the catalyst to produce the required octane level wascompensated for by raising the temperature. This adjustment, however,produced only a temporary solution since at the higher temperature thedecline in the catalysts activity was even more rapid than at theinitial reaction temperature and thus progressively higher temperaturelevels were required with increasing frequency. It is obvious that thistype operation quickly leads to a situation whereby it is impossible toobtain added octane improvement by raising the temperature, since thedecline in activity of the catalyst outstrips the ability of theoperator to compensate therefor. The sum total of these factors is thatwith the prior art catalysts operations for required high octane levelsresult in plant runs of a duration too short to be feasible forcommercial operation.

The requirements, therefore, of a catalyst which can be usedcommercially for producing fuels of the required high octane levels arethat it either be capable of producing the required octane level at arelatively low temperature or, in the alternative, that it be capable ofmaintaining its activity for long periods of time at extremely hightemperature levels. The catalyst of the instant invention has been foundto possess both of these requirements to an extremely high degree.Although the reasons for these unexpected and novel properties of theinstant catalyst are not known, several theories may be advanced as apartial explanation therefor. When catalysts are prepared in accordancewith the present invention, the platinum apparently is located in theneighborhood of the most catalytically active sites on the acidic metaloxide components, whereas with the prior art catalysts only that portionof the platinum as governed by probability considerations would belocated near such active centers since such methods involved meremechanical deposition. Moreover, it is apparent that in the preparationof the instant catalyst something more than base exchange is involvedinasmuch as other platinum compounds wherein the platinum is in thecationic portion of the molecule, and therefore theoretically may bedeposited on the acidic metal oxide component by base exchange, do notexhibit the properties of the instant catalyst as will be demonstratedhereinafter in the examples.

From the data in the examples which follow the accompanying drawingswere constructed. In the drawings:

Figure 1 is a plot of the D+L of the silica-alumina component versuspercent decrease in yield from maximum.

Figure 2 is a plot of the partial relative stability numher for thedehydrogenation reaction contribution (minimum bed temperature increase)versus minimum bed temperature increase as determined in the laboratoryreforming stability test.

Figure 3 is a plot of the partial relative stability number for theoctane number contribution versus the clear octane number decrease asdetermined in the laboratory reforming stability test.

The examples which follow are provided for the purpose of illustratingthe various aspects of the instant in vention and to demonstrate thesuperiority of the catalysts of the instant invention over the catalystsof the prior art.

In order to demonstrate the importance of the D+L rating of the acidicmetal oxide component and the necessity of employing an acid metal oxidecomponent within the range of 20 to 65, the following experimentsoutlined in Example I were carried out.

EXAMPLE I A number of catalysts were prepared wherein the D+L of thesilica-alumina component prior to platinization was varied over a widerange. A large commercial sample of silica-alumina cracking catalyst wasprepared by adding sulfuric acid to commercial water glass in an amountsufiicient to precipitate silica hydrogel. The silica hydrogel waswashed with acidulated water to remove sodium ions and then the hydrogelwas dispersed in an amount of an aqueous solution of aluminum sulfate ofsuitable concentration such that when ammonium hydroxide was added toprecipitate the alumina there was formed a silica-alumina compositecontaining approximately 13 percent by weight of alumina. Thesilicaalumina composite was then washed, dried, pelleted and calcined at600 F. to 900 F. This cracking catalyst had a D-l-L rating of about 93,according to the above described Birkhimer et al. method. Severalportions of the thus prepared silica-alumina component were then treatedwith steam at 1050 F. to 1250 F. and at 15 to 200 pounds per square inchfor 3 to 18 hours to obtain components having the D+L ratings indicatedin Table I. The different samples of the silica-alumina composites wereimpregnated with the platinous tetrammine complex ion in order to givebetween 0.5 percent 0.7 percent platinum on the finished catalyst. Thecatalysts were tested in a semi-plant scale unit wherein sulficientproduct was produced to obtain accurate yieldoctane data. The feed stockto the test unit consisted of a typical East Texas distillate having thefollowing properties.

AST M distillate:

Overpoint F 180 50 percent F 255 95 percent F 335 End point F 380 Clearoctane number (ASTM Method D908-53) 55 API gravity at 60 F 56.3

Prior to introduction into the unit the feed was preheated to varioustemperatures ranging between 750 F. and 940 F. in order to give a rangeof octane levels and yields corresponding to such octane levels. Liquidhourly space velocities of 3 and of 6 were employed at the varioustemperatures and sutficient recycle hydrogen was introduced with thefeed to maintain a hydrogen to hydrocarbon mol ratio of 10 to 1 at apressure of 500 pounds per square inch.

It was found that with silica-alumina components in the range of about20 D+L to about 45 D+L the yields of reformed product (volume percentfive-carbon atom and higher hydrocarbons based on fresh feed), for anyparticular octane number level, were equal and at a maximum. Withsilica-alumina components having .l'lH-L ratings above 45 the yieldswere below this maximum for any constant octane number level. Table Ishows the percent yield dei'iation from the maximum for the catalystsprepared and tested as described above for two different octane numberlevels.

Table I D-I-L of the Percent Clear Octane Number CFRR Silica-AluminaDecrease in (ASTM Method D9G8-53) Component Yield from Maximum 0 0 0 02. 6 4. 7 8. 4 88 10.6 93 Unsteamed..- 12. 1

These data are plotted in Figure 1 of the drawings. It is to be notedthat the catalysts produced from silicaalumina components having D+Lratings between about 20 and about 45 all give the maximum yield at thesame octane level, and consequently the slope of the curve in this areais zero. With catalysts produced from silicaalumina components havingD-f-L ratings between about 45 and 65 the yields obtained drop below themaximum and accordingly the slope of the curve increases in this area toa maximum at about 65 D-l-L. Catalysts prepared from components havingD+L ratings greater than 65 and up to the 90-95 level (corresponding toa freshly prepared, unsteamed component) produce yields which deviatefrom the maximum in direct proportion to the D+L rating of the componentand hence from 65 D+L to 90-95 D+L the curve forms a second straightline with a maximum slope. The straight line portions of the curve havebeen extended in the form of dotted lines to show the area of deviationfrom the constant slope lines.

It is apparent from this curve that catalysts prepared from componentsranging between 20 and 45 D+L are capable of completely controlling thehydrocracking reaction and maintaining a balance between it and theother reforming reactions, while between 45 and 65 some ability tocontrol the hydrocracking reaction is lost. Catalysts prepared fromcomponents having D+L ratings in excess of 65, however, were found tohave no ability to control the hydrocracking reaction as evidenced bythe fact that the loss of yield varies directly with the activity of thebase component. Accordingly, this curve demonstrates the necessity forusing acidic metal oxide components having D+L ratings below 65, asmeasured by the Birkhimer et al. method.

Catalysts prepared from components having D+L ratings less than 20 arenot preferred since they do not have suificient activity to produce theoctane level gasolines required by present day automotive engines.

In the following examples a number of catalysts were prepared bothaccording to prior art methods and according to the method of theinstant invention. In order to show the superior stability of thecatalysts of the instant invention, all of the catalysts were testedaccording to a standard reforming test procedure in the laboratory sinceit was obviously impractical to test every experimental catalyst in afull scale or commercial reforming operation.

In the laboratory reforming stability test a cc. portion of the catalystis placed in a fixed bed in the form of discrete pellets (8-12 mesh,U.S. standard) and an East Texas distillate having the followingproperties.

Endpoint F 365 Clear Octane Number (AST M Method D908-53)..- 55 APIgravity at 60 F 56.5

is passed thereover under the following conditions:

Inlet temperature to the catalyst bed and outlet temperature from thecatalyst bed is maintained at 875 F. for 24 hours, and then is raised to940 F. for the remainder of the test; hourly liquid space velocity is 3;pressure is 500 pounds per square inch; hydrogen to by drocarbon mol.ratio is to 1. Samples of product are taken at regular time intervalsduring the run, and their octane numbers determined. The difference inoctane number of the product after the catalysts have been on stream for72 hours and after 200 hours at a constant average catalyst bedtemperature is utilized as a part of the measure of the catalyststability as will be shown hereinafter.

The reactor consists of a metal tube surrounded by heaters to maintainapproximately isothermal conditions. A thermocouple well is placed atthe center of the reactor so that the temperature of the catalyst bedcan be determined throughout its length. It is a characteristic of thereforming process using a fixed bed reactor with a platinum on metaloxide component type catalyst that at a point near the top of thecatalyst bed the temperature of the catalyst will be at a minimum, whichtemperature is somewhat lower than either the inlet or outlettemperatures heretofore mentioned. The explanation for this minimum inthe catalyst bed temperature is relatively simple. As has been noted,one of the most important and also most rapid reactions in catalyticreforming is the dehydrogenation reaction, i.e., the conversion ofnaphthenes to aromatics. This reaction is highly endothermic, that is,it utilizes rather large amounts of heat. Inasmuch as it is a reactionthat proceeds rapidly, it reaches its maximum rate at a point near thetop of the catalyst bed and, under the specified experimentalconditions, it removes heat faster than it can be supplied with theresult there will be a minimum in the temperature profile of thecatalyst bed at the point where the dehydrogenation reaction is at itsmaximum. With a catalyst of high stability, since the heat input andother conditions are constant, this minimum bed temperature, as it willbe referred to hereinafter, will remain at nearly a constant value.Obviously, if the catalysts ability to promote the dehydrogenationreaction declines during its life, less dehydrogenation will occur andtherefore less heat will be utilized, with the result the minimum bedtemperature will rise. Consequently, the increase in minimum bedtemperature gives very important information as to the stability of thecatalyst under test.

As noted hereinbefore, the difference in octane value of the productafter the catalyst has been on stream for 72 hours and after 200 hoursis noted. This difference, while of obvious value in judging stability,might possibly be misleading if used as the sole criterion forstability. It might be misleading for example, if a catalyst started outwith good over-all reforming characteristics, but later lost its abilityto dehydrogenate while greatly increasing the hydrocracking reaction.The hydrocracking reaction will of course raise octane values, but atthe expense of producing large amounts of low molecular weight compoundsnot useful in gasoline. Thus, in the above example, while the octanedecrease might be small indicating a relatively stable catalyst,actually such a catalyst could have relatively poor stability.Therefore, by using a combination of minimum bed temperature change andoctane value change over the period of test, a much more reliable andaccurate measure of catalyst stability for reforming can be obtained.

The above described test gives an accelerated decrease in stabilitybecause of the extremely severe temperature levels used. In commercialplant operation, of course, much lower severities are used hence thedecrease in octane number with time and decrease in the dehydrogenationreaction with time are considerably more. gradual. Thus, although in thelaboratory test octane number declines of several units may beexperienced in the 128 hour test period, such declines require weeks ormonths in actual commercial operation. The correlation of theaccelerated laboratory stability test has been found to be very good,however, with regular plant runs. Inasmuch as the changes noted in theshort time period of the laboratory test require much longer periods inplant scale operation, it follows that small dilferences betweencatalysts as measured in the laboratory test will represent largedifferences in plant operation.

A method has been devised which not only makes use of the difierencefound between actual catalysts tested in laboratory and expresses suchdifferences in terms of relative stabilities, but which also comparesthe relative stabilities of actual catalysts with a theoreticalcompletely stable catalyst as a standard.

If a catalyst were completely stable it would, of course, show neitheran octane number decrease nor a minimum bed temperature increase whentested in the above described laboratory reforming stability test. Forpurposes of the comparison, this standard or perfect catalyst isassigned a total relative stability number of 100. Actual catalystsobviously will have total relative stability numbers less than thetheoretical value of 100, since they will show a minimum bed temperatureincrease and an octane number decrease. It is to be noted, however, thatboth factors contribute to the total stability of the catalyst;accordingly, a partial relative stability number is given to each, thesum of such partial relative stability numbers being the total relativestability number.

Since, as has been pointed out, dehydrogenation reaction stability is ofprimary importance, the relative contribution of dehydrogenationreaction stability (measured by minimum bed temperature increase) to thetotal relative stability is greater than the contribution of the octanenumber stability to the total relative stability. In order to properlyweigh these relative contributions, a value of 60 was selected for thepartial relative stability number of the dehydrogenation reactionstability contribution and'a value of 40 for the partial relativestability number of the octane number in the case of the standardcatalyst. These partial relative stability numbers for actual catalystsare in the same ratio, but obviously less than the standard values of 60and 40, respectively.

It has been found that a commercially acceptable catalyst when tested bythe laboratory method showed a minimum bed temperature increase betweenthe 72nd hour and 200th hour of 6 F., and an octane number declineduring the same time period of 3. This present commercially acceptablecatalyst was assigned a total relative stability number of 50.

From these data the plots in the accompanying drawings were constructed.

Referring now to Figure 2 of the drawings where the partial relativestability number for the dehydrogenation reaction stability contributionis plotted along the ordinate and the minimum bed temperature increaseis plotted along the abscissa, the abovementioned standard catalyst,designated Catalyst S, is located, of course, at 60 on the ordinate ofthe plot, as shown. The abovementioned commercially acceptable catalyst,designated Catalyst A, which was prepared by impregnating asilica-alumina component having a D+L of about 42 with chloroplatinicacid to give a finished catalyst containing 0.45 percent platinum(details of preparation are the same as details for Catalyst No. 1,below, except platinum content) having a minimum bed temperatureincrease of 6, has a partial relative stability number for thedehydrogenation reaction stability contribution of 30 calculated by: 60/(dehydrogenation reaction contribution) times 50 (total relativestability number of commercially acceptable catalyst) equals 30.

contribution is plotted along the ordinate and octane decline is plottedalong the abscissa, the above-mentioned standard, Catalyst S, is locatedat 40 on the ordinate of the plot, as shown. The commercially acceptablecatalyst, Catalyst A, having an octane number decline of 3, has apartial relative stability number for the octane number contribution of20 calculated by: 40/ 100 times 50 equals 20. Thus, the point forCatalyst A is located on the plot of Figure 3.

Correlation lines, C and D in Figures 2 and 3 respectively, are drawnthrough the points located on the plots. Having determined these lines,the stability of each catalyst can be compared with the stability ofevery other catalyst by utilizing the data obtained in the standardreforming stability test.

Obviously, if the correlation lines are extended below the points forCatalyst A on, the plots, they can be used to rate catalysts somewhatpoorer than commercially acceptable catalysts.

In order to prepare a series of catalysts for stability comparison, aquantity of a fresh commercial silicaalumina cracking catalyst wasprepared as described in Example I above in the form of cylindricalpellets inch in diameter and inch. high having a D+L rating of 93.Several portions of this component were treated with steam at a pressureof 150 pounds per square inch and at a temperature of 1050 F. forvarious times until the D+L of the silica-alumina was reduced to thevarious values indicated in the examples.

EXAMPLE II A portion of the silica-alumina component prepared asdescribed above having a D+L of 42.4 was contacted with an 0.026 molaraqueous chloroplatinic acid solution, 1.2 cc. of solution being used pergram of pellets. This solution was allowed to remain in contact with thesilicaalumina for about 24 hours at approximately 210 F. to 212 F. Theimpregnated pellets of silica-alumina were then dried in a stream ofnitrogen at a temperature somewhat above 212 F., following which theplatinum was reduced to the metallic state with hydrogen at 250 F. Theplatinum content of the finished catalyst was 0.48 percent by weight.This catalyst, designated at Catalyst No. 1, corresponds to a commercialreforming catalyst.

EXAMPLE III A second portion of the silica-alumina component having aD+L of 42.4 was treated with an 0.0214 molar aqueous solution ofplatinous tetramminochloride, [Pt(NH ]Cl together with sufi'icientammonium hydroxide to raise the pH of the solution to 11.1, the amountof solution being 1.2 cc. per gram of silica-alumina. The ammoniumhydroxide was added since, in order to impregnate an acidic metal oxidecomponent with this compound, it is necessary to raise the pH to a highlevel. The

platinum.

EXAMPLE IV A third. portion of the silica-alumina component having a D+Lof 40.3 was treated with an 0.0203 molar aqueous solution of platinoustetramminohydroxide,

[Pt(NH ](OH) for 18 hours at 212 F. The amount of solution" used was1.2' cc. per gram of silica-alumina.

The solution was drained from the impregnated silicaalumina componentand the component then was dried in a stream of nitrogen at atemperature in excess of 250 F. The platinum was reduced to the metallicstate with hydrogen at about 950 F. The finished catalyst containedabout 0.465 percent of platinum by weight and is designated as CatalystNo. 3.

EXAMPLE V A fourth portion of the silica-alumina component having a 7-L45 was treated with platinous tetramminohydroxide by the methoddescribed in Example IV to give a finished catalyst, Catalyst No. 4,having 0.355 percent by weight of platinum.

EXAMPE VI A fifth portion of the silica-alumina component having a D+Lof 40.3 was contacted with an 0.0276 molar aqueous solution of platinoustetramminohydroxide in the proportions of 1.2 cc. of solution per gramof silicaalumina component. The solution was held in contact with thecomponent for 18 hours at 212 F. The impregnated silica-alumina pelletswere drained and dried at 250 F., then the dried impregnated pelletswere calcined with air at a temperature of 650 F. to 700 F. for twohours. The finished catalyst, Catalyst No. 5, contained 0.620 weightpercent of platinum.

EXAMPLE VII A sixth portion of the silica-alumina component having a D+Lof 59.1 was treated with an 0.036 molar aqueous solution of platinoustetramminohydroxide for 18 hours at 212 F. The amount of solution usedwas 1.2 cc. per gram of silica-alumina. The solution was drained fromthe impregnated component and the component was then dried at about 250F. The dried impregnated pellets were then calcined With air at 650 F.to 700 F. to convert the platinum component to metallic platinum. Thefinished catalyst, Catalyst No. 6, contained 0.79 percent by weight ofplatinum.

Each of the catalysts prepared above was tested by the above describedlaboratory reforming stability test. It should be noted that each of thecatalysts raised the clear octane number of the standard charge stockfrom 55 to about to 92 (at the 72 hour point) as measured by ASTM MethodD9085 1. The results of the test and the stabilities found from Figures2 and 3 for the catalysts are set forth in Table II:

It is evident from the above data that the use of platinoustetramminohydroxide for impregnating an acidic metal oxide componentproduces a catalyst having a very markedly improved stability. Forexample, a catalyst of the present invention shows a 60 percent increasein stability over present commercially acceptable catalysts prepared byimpregnation with chloroplatinic acid, comparing catalyst Nos. 3 and 5with Catalyst No. 1. The catalysts of the present invention show abouttwice the stability of catalysts prepared by impregnation with platinoustetramminochloride, Catalyst No. 2.

The data also show that a catalyst prepared according to the instantinvention is 30 percent more stable 13 than a commercial catalystcontaining over 30 percent moreplatinum, comparing Catalyst No. 4 withCatalyst No. 1. Consequently, the present invention permits veryimportant savings in catalyst cost both by using less platinum on thecatalyst and by providing catalysts having greatly increased life.

In order to demonstrate further the superiorty of the instant invention,comparative runs were made in a com mercial catalytic reforming planthaving a capacity of about 2500 barrels per day.

This plant was first operated with the best available regular commercialcatalyst prepared according to the method of Example II whereinchloroplatinic acid was used for impregnating the silica-alumina. Thenthe plant was operated on a catalyst of the instant invention preparedby the method of Example VII wherein platinous tetramminohydroxide wasemployed in impregnating the silica-alumina base. The charge stock tothe plant was a blend of Western and Pennsylvania straight run naphthashaving the following properties.

ASTM distillation:

The operating conditions were: 600 p.s.i. pressure, 17:1 hydrogen tohydrocarbon ratio, and 3 space velocity. The average reactor inlettemperature was varied to produce regular and premium gasoline grades.

With the regular commercial catalyst the average reactor inlettemperature was raised to 930 F. in an attempt to make a 95 octaneproduct (with 3 cc. TEL/gallon), however, the maximum octane obtainedunder these conditions was 94.0 octane (with 3 cc. TEL.) and the octanedecreased rapidly with time at this temperature showing that thecatalyst was not stable. After operation under these conditions forthree days, the temperature was lowered to 885 F. to produce regulargrade gasoline of 89-90 octane (with 3 cc. TEL/ gallon). It wasnecessary to raise the average reactor inlet temperature by incrementalamounts to maintain this octane level until a final temperature of 935F. was reached after 27 additional days of operation at which time thecatalyst was completely deactivated and required regeneration. Followingregeneration a second attempt was made to make premium grade gasoline,95 octane, but even at temperatures as high as 935 F. to 940 F. theproduct was only 93 octane (with 3 cc. TEL/gallon).

Following the test run with the regular commercial catalyst, at secondtest run was conducted wherein the same feed stock previously describedwas treated with the above mentioned catalyst of the present inventionunder substantially the same conditions of pressure, hydrogen tohydrocarbon ratio and space velocity employed in the first test run. Asin the first test run the average reactor inlet temperature was variedto produce regular and premium grade gasoline.

After 10 days of operation at a temperature of about 860 F., duringwhich period regular grade gasoline having an octane rating between 89and 91 was produced, the average reactor inlet temperature was raised to910 F. to produce a 95 octane (with 3 cc. TEL/ gallon) gasoline.Following 4 days of operation at this premium octane level, thetemperature was intermittently lowered and raised for a further periodof 46 days, during which period regular and premium grade gasolines werealternately produced at average temperatures the same as or below thoseemployed in the beginning of the run, i.e. 860 F. for regular and 910 F.for premium. At the end of the stated period of alternate operationwhich covered a total of 61 days a slightly higher temperature wasrequired to produce 95 octane gasoline, however, after 5 days at thislevel, about 920 F., the temperature was lowered to produce regulargrade gasoline at 860 F. and operation under these conditions was beingmaintained after 93 days.

The last run described clearly demonstrates the phenomenal stability ofthe catalyst of the present invention. It is to be observed from theresults of this run that after several months of operation at normalrefinery practice, ie. alternate production of regular and premiumgasolines with the amount of premium being produced being between 20percent and 30 percent of the total, the novel catalyst of thisinvention showed practically no deactivation as evidenced by the factthat the temperatures required to obtain regular and premium gradegasolines were substantially the same throughout the entire period ofoperation. In addition, the temperatures required to produce eitherregular or premium grade gasoline were substantially lower when usingthe catalyst of the instant invention as contrasted to the commercialcatalyst preprepared by depositing chloroplatinic acid on thesilicaalumina base, which catalyst, of course, was not capable ofproducing premium grade gasoline from this feed stock.

Furthermore, the test run on the platinous tetramminohydroxideimpregnated catalyst of this invention had a better yield-octanerelationship than the regular commercial catalyst. At the premium gradelevel, 95 octane, the instant catalyst gave a 3 percent better yield ofgasoline than the regular commercial catalyst and at regular gradegasoline level, octane, the instance catalyst gave about a 2 percenthigher yield of gasoline than the regular commercial catalyst. Thecomparison at the premium grade level could be obtained only byextrapolation of the yield-octane curve for the regular commercialcatalyst since it, of course, only produced gasoline of 94 octane withthis feed stock during the first test run.

Accordingly, these actual plant runs prove conclusively that thecatalysts of the instant invention not only have a stability farsuperior to previously known catalysts, but also are capable ofproducing a higher octane level product with a higher yield thanpossible with the prior art catalysts.

The method of the instant invention has been found to be effective inthe preparation of reforming catalysts for treatment of petroleumdistillates, such as light hydrocarbons, naphtha, gasoline and kerosine,and particularly gasoline fractions. The fractions may have an initialboiling point within the range of 50 F. to 90 F. and an end boilingpoint of about 425 F. to 560 F.

It is preferred when reforming petroleum distillates boiling in thegasoline-kerosine range to utilize reaction temperatures within therange of 600 F. to 1000" F., pressures of from 100 to 1000 pounds persquare inch, liquid hourly space velocities of from 0.1 to 10 andhydrogen to hydrocarbon mol. ratios of from 1 to 20 mols. of hydrogenper mol. of hydrocarbon.

We claim:

1. A method of manufacturing a catalyst which comprises impregnating anacidic metal oxide component with an aqueous solution of platinoustetramminohydroxid-e, drying the impregnated acidic metal oxidecomponent and converting the platinum impregnated on the acidic metaloxide component to the metal, said acidic metal oxide component beingcharacterized by having a catalytic cracking activity within a rangebetween 20 and 65 as compared with a theoretical maximum catalyticcracking activity of 100 and practicable maximum catalytic crackingactivity of between 90 and 95 on a distillate-plus-loss scale for themeasurement of the catalytic cracking activity of a cracking catalyst.

2. A method of manufacturing a catalyst which comprises contacting anacidic metal oxide component with an aqueous solution of platinoustetramminohydroxide at an elevated temperature to impregnate the acidicmetal oxide component, drying the impregnated acidic metal oxide.component, and: converting the platinum impreg: nated on the acidicmetal oxidecomponent to the metal, said acidic metal oxide componentbeing characterized by having a catalytic cracking activity Within arange between and 65 as compared with a theoretical maximum catalyticcracking activity of 100 and a practicable maximum catalytic crackingactivity of between 90 and 95 on a distillate-plus-loss scale for themeasurement of the, catalytic cracking activity of a cracking catalyst.

3. A method of manufacturing a catalyst which comprises impregnatingsilica-alumina with an aqueous solution of platinoustetramminohydroxide, drying the impregnated silica-alumina andconverting the platinum impregnated on the silica-alumina to the metal,said silicaalumina .component being characterized by having a catalyticcracking activity within a range between. 20, and65.

ascomparediwith a theoretical maximumcatalytic cracking activity of 100and a practicable maximum catalytic cracking activity of between 90 and95 on a distillateplus-loss scale for the measurement of thecatalyticcrackingactivity of a cracking catalyst.

4. The catalyst prepared by the method of claim 3.

5. A method of manufacturing a catalyst which comprises contactingsilica-alumina with an aqueous solution of platinous tetramminohydroxideat an elevated temperature to impregnate the silica-alumina, drying theimpregnated silica-alumina and converting the platinum impregnated onthe silica-alumina to the metal, said silicaalumina component beingcharacterized by having a catalytic cracking activity within a rangebetween 20 and 65 as compared with a theoretical maximum catalyticcracking activity of 100 and a practicable maximum catalytic crackingactivity of between 90 and 95 on a distillateplus-loss scale for themeasurement of the catalytic cracking activity of a cracking catalyst.

6. A process for reforming a petroleum distillate fraction boilingwithin the gasoline-kerosine range to increase the anti-knock valuethereof which comprises subjecting said fraction to contact at reformingconditions in the presence of hydrogen with a catalyst prepared bycontacting at an elevated temperature a silica-alumina component with anaqueous-solution of platinous tetramminohydroxide to impregnate thesilica-alumina, drying the impregnated silica-alumina and converting theplatinum impregnated on the silica-alumina to the metal, the platinumbeing in an amount between 0.1 to 2.5 percent by weight of the finalcatalyst, said silica-alumina component being characterized by having acatalytic cracking activity within a range between 20 and as comparedwith a theoretical maximum catalytic cracking activity of 100 and apracticable maximum catalytic cracking activity of between and on adistillate-plus-loss scale for the measurement of the catalytic crackingactivity of a cracking catalyst- 7. A process for reforming a gasolinefraction to increase the antiv-knock value thereof which comprisessubjecting said fraction to contact at a temperature within the range of600 to 1000 F., a pressure of from to 1000. pounds per square inch and aliquid hourly space velocity of from 0.1 to 10, in the presence of from1 to 20 mols. of hydrogen per mol. of hydrocarbon with a catalystprepared by contacting at an elevated temperature a silica-aluminacomponent with an aqueous solution of platinous tetramminohydroxide toimpregnate the silicaalumina, drying the impregnated silica-alumina andconverting the platinum impregnated on the silica-alumina to the metal,the platinum being in an amount between 0.1 to 2.5 percent by weight ofthe final catalyst, said silicaalumina component being characterized byhaving a catalytic cracking activity within a range between 20 and 65 ascompared with a theoretical maximum catalytic cracking activity of 100and a practicable maximum catalytic cracking activity of betwen 90 and95 on a distillate-plusloss scale for the measurement of the catalyticcracking activity of a cracking catalyst.

References Cited in the file of this patent UNITED STATES PATENTS2,623,860 Haensel Dec. 30, 1952 FOREIGN PATENTS 715,739 Great BritainSept. 22, 1954 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIONPatent No.0 2,884,374 April 28, 1959 James E.,, Connor, Jr et ale 5 inthe printed specification It is hereby certified that error appear ofthe above numbered patent requiring correction and that the said LettersPatent should read as corrected below.

Column 11, line 47, for "designated at" read designated as column 14,line 19 after "catalyst" strike out "pra "o Signed and sealed this 18thday of August 1959 (SEAL) Attest:

KARL Ii, AXLINE ROBERT C. WATSON Commissioner of Patents AttestingOfficer

7. A PROCESS FOR REFORMING A GASOLINE FRACTION TO INCREASE THEANTI-KNOCK VALUE THEREOF WHICH COMPRISES SUBJECTING SAID FRACTION TOCONTACT AT A TEMPERATURE WITHIN THE RANGE OF 600 TO 1000*F., A PRESSUREOF FROM 100 TO 1000 POUNDS PER SQUARE INCH AND A LIQUID HOURLY SPACEVELOCITY OF FROM 0.1 TO 10, IN THE PRESENCE OF FROM 1 TO 20 MOLS. OFHYDROGEN PER MOL. OF HYDROCARBON WITH A CATALYST PREPARED BY CONTACTINGAT AN ELEVATED TEMPERATURE A SILICA-ALUMINA COMPONENT WITH AN AQUEOUSSOLUTION OF PLATINOUS TETRAMMINOHYDROXIDE TO IMPREGNATE THESILICAALUMINA, DRYING THE IMPREGNATED SILICA-ALUMINA AND CONVERTING THEPLATINUM IMPREGNATED ON THE SILICA-ALUMINA TO THE METAL, THE PLATINUMBEING IN AN AMOUNT BETWEEN 0.1 TO 2.5 PERCENT BY WEIGHT OF THE FINALCATALYST, SAID SILICAALUMINA COMPONENT BEING CHARACTERIZED BY HAVING ACATALYTIC CRACKING ACTIVITY WITHIN A RANGE BETWEEN 20 AND 65 AS COMPAREDWITH A THERETICAL MAXIMUM CATALYTIC CRACKING ACTIVITY OF 100 AND APRACTICABLE MAXIMUM CATALYTIC CRACKING ACTIVITY OF BETWEEN 90 AND 95 ONA DISTILLATE-PLUSLOSS SCALE FOR THE MEASUREMENT OF THE CATALYTICCRACKING ACTIVITY OF A CRACKING CATALYST.